Method of forming teeth on gears



METHOD OF FORMING TEETH 0N GEARS Filed June 25, 1923 5 -s t 1 INVENTOR M}, W,

A TTORNEK Dec 22, 1925.

H. N. ANDERSON METHOD OF FORMING TEETH ON GEARS Filed June 25, 1923 6. Sheets-Sheet 2 IN VEN TOR ATTORNEY Dec. 22, 1925.

' H. N. ANDERSON METHOD OF FORMING TEETH ON GEARS 6 Sheets-Sheet 5 y I +2 W O Mm 2 I E vQ O v2 O W2 w w, O

Dec. 22, 1925. 1,566,951

H. N. ANDERSON -METHOD OF FORMING TEETH ON GEARS Filed June 25, 1923 6 Sheets-Sheet 4 Dec. 22, 1925.

H. N. ANDERSON METHOD OF FORMING TEETH ON GEARS Filed June 25, 1925 6 sheets-Sheet 5 LI/YE w 2 3M 6 3 7 m 9 0 6 7 B IN VEN TOR A TTORNEY.

Dec. 22, 1925-.

H. N. ANDERSON METHOD OF FORMING TEETH ON GEARS Filed June 25, 19 6 Sheets-Sheet V I c I I Patented'Dec. 22, 1925.

HAROLD N. ANDERSON, or CLEVELAND, 'oHI'o.

METHOD OF FORMING TEETH ON GEARS.

Application filed June 25,

To all whom it may concernc Be it known that I, HAROLD N. ANDERSON,

' a citizen of the United States, residing at Cleveland, in the county of Cuyahoga and State of Ohio, have invented a new and useful Method of Forming Teeth on Gears, of which the following is a specification.

My present invention relates to rolling teeth on gears by a new method.

In United States Patent No. 1,001,7991 showed a machine for rolling spur gears, using first a toothed breaking-down roll and then a toothed finishing roll" for forming teeth on a heated gear blank. While it was intended that this machine should operate continuously in one direction, I suggested that in order to effect certain results the direction of rotation might be reversed at some point in the operation. In United States Patent No. 1,240,915 I showed a machine for rolling spur gears with a single toothed die roll, this machine also being intended to operate in one direction. In United States Patents Nos. 1,240,914; 1,240,916; 1,240,917 and 1,240,918 I showed machines for rolling bevel gears with dierolls rotating in one direction. In United States Patent No.'1, 240,913 I showed a machine for rolling spur gears with areciprocating rack, which, of course, necessitated I oscillatory motion of the blank. In the machine of this patent the blank was caused to periodically advance with reference to the tooth-forming rack, which necessitated periodical separation of the rack and blank. In these various machines teeth were formed on the blank by pressing the die and rotating blank together, gradually sinking the die teeth into the blank to the required depth,

forming the teeth by generating principle. My present invention consists in forming teeth on the blank by oscillatory rotation of the blank in contact with a rotary die, an-

' gular advance of the blank and die being effected by always moving them through more degrees in one direction than in the other direction.

In United States Patent No. 1,237,125, I explained the action of the die teeth as they enter and leave the blank, and pointed out? that because the die teeth move toward the axis of the blank on entering and away from the axis on leaving the space between the teeth, there is a slight though negligible what is known as the 1923. Serial No. 647,596.

difference in the effect produced on the two sides of the spaces. As was there stated this difference is neutralized in the machine disclosed in Patent No. 1,240,913, where the teeth are generated with a reciprocating rack. The principal object of the present invention is to provide means for employing this reciprocatory method in connection with a rotary die, and also to adapt it to rolling bevel and other types of gears as well as spur gears.

' In the accompanying drawings I have shown two embodiments of my invention, each adapted to roll bevel gears. The first of these is disclosed in my co-pending application, Serial No. 410,866, and is illustrated in Figs. 1 to 7, inclusive, in which,

Fig. 1 is a plan view of the machine;

Fig. 2 is a rear elevation of a portion of the machine shown in Fig. 1, it being the mechanism by which the die and blank are oscillated; v

Fig. 3 is an elevation, principally in section, of the mechanism for rectifying the direction of rotation of the cam by which the die roll is moved toward the blank;

Fig. 4 is a transverse section of the mechanism shown in Fig. 3, taken on line 4-4;

Fig. 5 is a front elevational view of a portion of the manually controlled clutch shifting mechanism;

Fig. 6 is a side elevational view of the mechanism seen in Fig. 5, and

Fig. 7 is a View of the cam by which the die is pressed into the blank.

In Fig. 8 I show another machine, in.

which an electric motor is made to oscillate, thus imparting oscillatory motion to the die and blank;

Fig. 9 isa detail, showing the construction of the parts carryin the die roll and blank, and

Fig. 10 "is a iagrammatic view of the electrical connections and switches for controlling the motor.

Referring now to the firstembodiment, particularly Fig. 1, the gear rolling portion of the machine is mounted on a base 25, while the driving mechanism is mounted on a base 26, the two bases being united at 27.

'A shaft 28 is mounted to rotate in bearings 29 and 30 carried by the base 25. At one of its ends this shaft carries a'timing ear 31. A superbase 32 is mounted on the base 25 and arranged to be swung to various position n thebase roun an axis show in dotted lines at 33. It is secured in any desired position on the base by means of bolts 34 whose heads are located in T slots 35 formed in the base 25. The superbase. carries bearings 36 and 37 in which is journaled a shaft 38. One end of this shaft carries a beveled .timing gear 39, which gear .is in mesh with the timing ear 31. The shaft 38 alsocarr ies a holder or supporting bevel gear blanks while teeth are bein rolled on them, a portion of this holdering seen at 40.

The shaft 28 is tubular and within it there is a shaft 45. This shaft is adapted to slide 'endwise in the shaft 28, but is attached to the. shaft 28 by splines (not shown) that cause the shafts 22 and to rotate as though they were one. Adjacent to one end of the shaft 45 is a follower 46 arranged to slide in guides 47 carried by the base 25, and

the shaft 45 and follower 46 are connected together by a suitable thrust bearing 48 which compels the shaft and follower to move as a unit, but allows the shaft to rotate with reference to the follower. A collar 49 is clamped on the shaft 45. and a similar scribed collar 50 is clamped on the end of shaft 28.

Between these collars a compression spring 51 is confined, which spring tends constantly to move the shaft 45 endwise in the shaft 28 in the direction that will carry the shaft 45 away from the blank holder 40. A roller 52 is mounted on the follower 46; the function of this roller will be described later. On the ,end of shaft 45, adjacent to the blank holder A jack shaft is mounted in bearingsl61 carried by the base 25, and a. bearing 62 carried by base 26, this shaft being connected to shaft 28 by bevel gears 63 and 64, the lat:

ter being keyed to shaft 28. The jack shaft 5 carries a bevel gear 65 which is enmeshed with two bevel gears, 66 and 67, mounted to rotate freely on a shaft 68, these gearsbeing on opposite sides of gear 65. This shaft is rotated constantly througha worm gear 69 by a motor 70, the motor shaft 71 and worm shaft (not shown), constituting what will presently be referred, to as the mam shaft.

Gears 66 and'67 are coupled alternately to the shaft 68 b means of clutches 72 and 73, the clutches constantly in one direction, the shaft 60 will be rotated in one direction by the clutch 72 and gear 66, and rotated in the opposite direction by the clutch 73 .and gear 6 For the purposeof rotating the jack shaft eing operated by ashifting mechanismthat will be described presently. 'It is evident that since the shaft 68 rotates 60 continuously in one direction I provide a I of sprockets and a chain. T e pulley 74 isconnected to the jack shaft when desired by a clutch 77.

The mechanism for operating the clutches 72 and 73'will nowbe described and in this connection reference will be had to Figs. 1

and 2. A shaft 80, mounted in bearings 81 carried by the base 26, is constantly rotated through a belt or chain 82 by the shaft 68.

Two cams, 83 and 84, are mounted on t he shaft 80 and while adapted to slide endwise on the shaftthey are compelled to rotate in .unison therewith by splines (not shown). The cams are connected through the medium of sleeves 85 to collars 86, these collars in turn, being connected to a fork 87 by means of links 88. The connection between the sleeves 85 and collars 86 is such as permits the sleeves to rotate in the collars while the latter remain stationary. The connection between the fork 87 and links 88 is effected by means of studs 89 fixed in the tines of the fork 87. These studs extend beyond the hubs of the links and into stationary guides .90. The fork 87 is fixed to the end of a rod 91 shown in dotted lines in Fig. 1, the other which the studs 83 carried by the tines of the I fork are the knuckles, and when the fork is moved to a position where the axes of the studs 89 intersect the axis of the shaft 80, in

otherwords, when the links 88 are moved to a position where they are in alinement with each other, the cams83 and 84 are moved on the shaft 80 into operative positions. They occupy this position in Fig. 2. the fork 87 is moved by the rod 91 and lever 92 to the position shown in Fig. 1, cams 83 and 84 are drawn toward each other by links 88 and out of operative positions. The clutches 72 and 73 are provided with the usual shifting collars 100, each of which is moved longitudinally on the shaft 68 by a shifting lever 101. these levers being mounted to rock on fixed centers 102. Each of the lovers carries a roller 103 that cooperates with one of the earns, 83 and 84. The levers '101 are connected togetherby arod 104 so that they movein 111118011.

When

Referring now to Fig. ,2 it will be seen that the cam 84 has rocked its lever 101 in the direction necess-arv to close the clutch 72; the gear 66 is therefore driving the gear 65 while the gear 67 is being driven idly by the gear 65 in a direction opposite to that in which the shaft 68 rotates, this being possible because the clutch 7 3-is open. When the shaft 68 has rotated a predetermined disgear opposite to that with which gear 66 meshes, it is seen that the gear 67 rotates the gear 65 in a direction opposite to that in which gear 66 drives it. When the shaft 68 has rotated a predetermined distance with the clutch 73 closed, the cam S-l again closes clutch 72, clutch 73 being simultaneously opened, and the direction of rotation of gear 65 is again reversed. In this way the gear 65 is driven automatically a predetermined distance in each direction, the

reversals being effected automatically as 4 long as the cams 83 and 84 remain in operative position. When the oscillatory motion has continued the desired length of time the shaft 93 is rocked, and through the medium of arm 92 and rod 91 the fork 87 is moved to the position shown in Fig. 1, thereby moving the cams 83 and 84 to their inoperative position. The sleeves 'extend beyond the cams 83 and 84 and at their ends 1% carry disks 94. Moving the links 88 to the position they occupy in Fig. 1, carries the sleeves toward eachother sufficiently so that the disk 94 will engage the lever 101 whose clutch happens to be closed and rock the lever far enough to open the clutch.

The mechanism for starting, stopping and controlling the machine will now be de scribed: The vertical shaft 93 is mounted to rock in a bracketcarried by the base 26. See Figs. 5 and 6. An arm 111 is keyed to the upper end of the shaft and it is provided with a recess 112 formed by two dcycndinglugs 113. A short distance below the hub of the arm 111 a similar arm 114, is loosely mounted on the shaft 93, the outer end of this arm having a recess 115 similar to recess 112 and also formed by lugs 113, these lugs, however, extend upward instead of depending. Secured to the hub of .the arm 114 is a sleeve 11 6 which extends downward on the shaft 93 a suitable distance and at its lower end carries a forked arm 117. Loosely mounted on the shaft 93' between the hubs of the arms 111 and 114 is a collar 11.8 to which is pivotally attached a lever 119. the pivotal axis being horizontal, so thatthe lever may be rocked upward or downward from a central or neutral position. The lever may also be laterally rocked because of the collar being loosely mounted on the shaft. Each of the arms, 111 and 114, carries a fiat spring 121. These springs bear against opposite sidesof the lever 119 and hold it in a central or neutral position. The forked arm 117 is connected to the clutch 77, so that when the arm 114 is rocked on the shaft 93 the clutch is opened or closed.

By referring to Figs. 5 and 6 it will be seen that the recesses 112 and 115 are opposite each other and that by rocking the lever 119 upward on its axis120 the lever maybe made to engage in recess 112. By rocking it downward it will engage in recess 115. \Vith the arms in the positions shown in these views all of the clutches are open. first rocked downward into the recess 115 and then swung to the left. To throw the oscillatory mechanism into operation the lever would be raised into the recess 112 and then thrown to the left, the iever is thus coupled at will to either arm. To prevent the lever from being disengaged from'either arm before the arm has been returned to its home position I provide a stationary locking bar 122 which is mounted on an extension 123 of the bracket 110. hen the lever 119 is engaged with one of the arms and thrown to the left the locking bar 122 prevents its disengagement from the arm without first being returned to the normal or home position. By this means closing the clutch 77 while the oscillatory mechanism is in operation, or throwing in the oscillatory operation while the clutch 77 is closed is prevented.

I shall now describe the mechanism for moving the shaft 45 longitudinally and pressing the teeth of the die roll into the heated blank in the holder 40. A shaft 130, rotating in bearings 131 on the base 25. has keyed to it a cam 132, and it is necessary to rotate this cam one revolution to roll each blank, moving it continuously in one direction, notwithstanding the other parts of the machine, even those parts which drive the cam. are oscillating part of the time. A worm gear 133 is keyed to the shaft and is driven by a worm (not shown) on the shaft 134, which rotates in bearings 135. A

shaft 136 in longitudinal alinement with shaft 134 rotates in bearings 137 and is driven by spiral gears'138 and 139. lVhen the jack shaft is being driven by the clutch 77 the shaft 136 drives shaft 134 through an automatic friction clutch (see Figs. 3 and 4). This will now be described.

In Fig. 3. it will be seen that the ends of the shafts 134 and 136 almost abut. Keved to the extreme end of the shaft 136 is a gear 140 having a hub 141 to which is keyed the member 142 of the automatic friction clutch, this being seen to the best advantage in Fig. 4. Keyed to the extreme end of the shaft 134 is a gear 143 having 'a hub 144.

To close the clutch 77 the lever/is Secured to this hub is a ring 145 which extends beyond the hub into the zone of the member 142. The member 142 is cut away at three points to form recesses 146 in which rolls 147 are confined. The faces 148 thus formed upon the member 142 are slightly eccentric and when the member 142 rotates in the direction ndicated by the arrow in Fig. 4 there is a tendency for the rolls to roll to higher points on the faces 148, which causes the rolls to become jammed between the faces 148 and the interior of the ring 145 and enables the member 142 to drive the ring 145. lVhen the member 142 rotates in the opposite direction to that shown by the arrow the rolls tend to roll to lowerpoints on the eccentric faces and thus relieve the pressure against the ring 145 and allow the member 142- to rotate freely within the ring. The rolls are constantly pressed toward the higher points of the eccentric faces by spring-pressed plungers 149, so that when the member 142 starts to rotate in the direction indicated by the arrow the rolls grip the ring 145 almost instantly, so that there is substantially no lost motion in that direc'tion by the member 142.

During the oscillatory operation of the machine the shaft 136 is oscillated along with the other parts of the machine. Half of the time, therefore, it is rotating in a direction opposite to that in which the clutch 77 drives it and at these times the member 142 -rotates in the direction opposite to that indicated by the arrow in Fig. 4. For the purpose of driving the shaft 134 at these times I provide a rectifying device, comprising a second automatic clutch mounted on a shaft 150. A. gear 15l,keyed to this shaft is driven by the gear 140 through an intermediate gear 152, shown also in dotted lines in Fig. 4. Keyed to a hub forming part of this gear is a clutch member 153, just like member 142 except. that'the eccentric faces face the opposite way. Loosely mounts ed on the shaft 150 is a gear 154 carrying a ring 155 similar to ring 145. Rolls 156' confined in the recesses perform the same function as rolls 147. When the shaft 136 rotates backward, that is, contrary to the direction in Wlllfll clutch 77 drives it, the gear 154 is frictionally driven bythis second clutch and it drives the gear 143 in the same direction that the member-142 drives it. It is. thus seen that whether the machine is oscillating or rotating continuously in one direction the shaft 134 is rotated forward, driving the cam 132 in the right direction alwaysf Fig, 7 is" an enlarged view of the cam 132 and in dottedlines a portion of the roller 52 is shown in the position-it occ'upies with reference to the cam when-a gear blank is being" placed in the holder 40. The follower 46 is constantly urged by the spring to move toward the cann'so that the roller 52 bears on;

the periphery of the cam at all times. lVh'en the blank has been secured in the holder'the operator raises the lever 119 and throws it' .to the left, thus putting into operation the oscillating mechanism, which causesrotat-ion of the cam in the direction indicated by arrows in Figs. 1 and 7. For purposes of explanation the cam is assumed to. be divided into several sectors; the action of the sector AB is to move the roller 52 a considerable distance toward the blank, which brings the die roll practically into engagement with the blank. The sector BC continues the movement of the die and causes the teeth to sink into the blank, the die and blank continuing to oscillate during this time. I prefer to time the oscillation so that the blank will rotate approximately from one to threerevolutions each way. This however is not essential and in some cases different timing may be found preferable. The timing may be varied bychanging the speed ratio of shafts 68 and 80. There are other ways of doing this of course, which any skilled mechanic would easily see. The angular advance in one direction of the die and blank may be effected in either of two ways: the clutches 7 2and 73 are friction clutches and therefore 'At' about the time the point C on the cam reaches the roller 52 the-operator will return the lever 119 to its central position, thereby stopping the oscillation of the machine, and he will then move the lever downward, thus coupling it to the arm 114, and throwing it to the left will close the clutch 77 and start the machine to rotating in one direction. As I the oscillating mechanism is driven through the worm gear 69 it is seen that the velocity at which the die and blank oscillate is much less than when they are being rotated by the clutch 77, for at that time the jack shaft isblank is effected by the sector C-D. This slight additional advance into the blank, ac compa'nied as it is by rapid rotation in'one direction, compactstthe metal of the teethand gives them the final and" correct form.

The sector DE simply holds the die at the final depth in the blank while the rapid roholder, the velocity of the cam varies just as' does that of the die and blank holder. It is seen, therefore, that while the char acterstics gun, the advance may be completed during the oscillatory 'operatlon. Furthermore, the continuous rotation may be omitted and the blank completed by oscillation alone. In fact, for some purposes I prefer to omit the continuous one-way operation.

It occasionally happens that a blank must be returned to the holder and rerolled. .In

2 such cases it is important to place the blank in the holder in ,a position where the die teeth will enter between the teeth which have been more or less completely formed on the blank. For this purpose I provide a lever 165 pivoted at 166, having an upwardly extending member 167 adapted to engage 2. lug 168 extending laterally from the follower 46.

. Ordinarily, the lever rests on a stop pin 169 and when it is necessary to use the lever this pin is removed, so that. the lever may be rocked downward, bringing the member 167 into engagement with the lug 168. Con/- tinned downward motion of the lever moves the shaft 45 and therefore the die toward the blank. The operator turns the blank in the holder to a position where the die teeth enter properly between the teeth of the blank and while pressing. the die gently against the blank and the blank into the holder by means of the lever 165, he clamps the blank in the holder; then when the blank is rerolled there is the minimum of disturbance of the teeth that were formed during the previous rolling. v

I shall now describe the machine shown in Fig. 8. In this machine, instead of the elec-- ginning the oscillatory #operation at the motor.

Referring now to 8 it will be seen that the parts of this machine are mounted upon a base 225. Many of the parts of this machine being exactly or substantially like the corresponding parts of the machine shown in Fig. 1, I shall use similar numbers on the parts of this machine, but

0 l meral 2, or in some cases t e numeral 3.

ihus a shaft 228 is mounted to rotate in I bearings 229 and 230 carried .kt ts right hand'end this tun ng gear 231, shown with dotted lines.

the base 225.

The superbase 232 is mounted upon the base 225 and arranged to swing to various sitions around an axis 233,v and is held in the desired position by bolts 234, the. heads of which reside in T slots 235 in the base 225. 'lhe'superbase carries bearing 236 and 237,

b shaft carries a L.

in which rotates a shaft 238. 'A timing gear 239secured to this shaft meshes with the timing gear 231. Thus the shafts 228 and 238 are made to rotate at a' fixed velocity ratio. I

The shaft 228 is tubular and within it there is a shaft 245. This shaft is connected by a spline 244 (Fig. 9) to the shaft 228, so, the two shafts will rotate in unison, as though they were integral, but the shaft 245 is left free to slide endwisein shaft 228. A follower block 246 is mounted to slide in guides 247 carried by the base 225, in a line parallel to the axes of the shafts 228 and 245, and the latter shaft is connected to the block 246 -by a thrust bearing 248, which enables the shaft to rotate with reference to the block. A collar 249 is secured to the end of the shaft 245 and a similar collar, 250, is secured to the end of the shaft 228, a compression spring 251 being confined between these collars. The collar 250 abuts the bearing 230, so the spring constantly tends to move the-shaft 245 toward the left as-it lies in Fig. 8, the block 246 being simultaneously moved by the thrust bearing 248.

The block 246 carries a roller 252, the pur- 239, the shaft 238 carries a holder 240 for a gear blank 241,- upon which teeth are to be rolled. See Fig. 9. The shaft 245 carries a die-roll 242, which when pressed against 20 the blank 241, the die and blank rotating at an invariablevelocity ratio, rolls teeth on the blank. This die-roll, blank holder, etc, are applicable to the machine shown in Fig.

1 as well as to that shown in Fig. 8. I have already described the mechanism of 1' for raduall ressing the die-roll into the bla and shall now describe the mech anism for this purpose in the structure shown in Fig. 8.

A shaft 330 rotating in bearings 331, car- .img

ries a cam 332, similar to 'cam 132 of Figs.

land 7. This shaft carries a worm gear (not shown) with which a worm. (also not shown) meshes, this'worm being carried by a shaft 334, whichrotates in bearings 335- 335. This shaft is composed of two parts, joined by a coupling 336. A motor 338,-:

mounted on the base 225, is connected}- to the shaft 334. It will be remembered that themotor is arranged to oscillate, while it'is necessary to rotate the cam. 332 in one direction only. Therefore the rectifying mechanism, which is slmllar to that shown in Eigsrl, 3 and 4,. is necessary, so that the shaft 334 will' rotate in the same direction whether the shaft 228 rotates in one direction or the other.

For the purpose of repeatedly reversing the direction of rotation of the motor, so as :to effect the oscillatory motion referred to,

I provide a commutator comprising a shaft 350, which is rotated in one directiononly by a sprocket chain from the shaft 334. This commutator is enclosed in a casing 351, so I shall describe and explain it in connection with Fig. 10. of the drawings. In'this figure, the motor, which is shown at 33 8, is started and-stopped by one or the other of two electrically operated switches, shown, respectively, at 353 and 354. For convenience I shall refer to switch 353% the forward switch and to 354 as the backward. These switches are relays, in fact. That is, they contain electro-magnets, or solenoids, which are energized by relatively small currents, and when energized these magnets operate the switch by which the current for operating the motor is controlled. They also control whatever resistance devices are needed in starting the motor, and if desired a dynamic brake for quickly stopping the motor. As switches of this kind are in common use and well known in the to this or any other particular type of motor.

' from, is an arm 360, carrying-wipers which Current for operating the motor is brought to the switches 353 and 354 by line wires 355 and 356. The commutator 352, which is merely diagrammatic, comprises a base composed of insulating material, on. which is mountedan 'annular contact plate 357 and two segmental contact lates, 358 and 359. Mounted on shaft 350, ut insulated therecontact with'the plates 357, 35s and 359.

Plate 358 is connected by a wire to the for v ward switch, 353,.and plate 359 is connected I by'awire tothe backward switch, 354. The

arm 360 is constantly in contact with plate 357. The annular plate 357 may be connected through a switch 361 and contact 362 to the line wire 356. In the diagram the arm 360 i is in contact with plate 359; therefore, if the .switch 361 is on the contact 362, switch 354 would be closed and the motor started to rotating backward. It will be remembered that the shaft 350 rotates in onedirection only. Therefore, the arm 360 will presently leave its contact with the segment 359 and come into contact with the segment 358, causing the switch 354 to open and the switch 353 to close, thus reversing the motor and causing it to rotate forward.

' In order to cause'an angular advance of the die andblank, the segment 358 extends fewer degrees than the segment 359. That is, the die and blank rotate backward farther than they rotate forward. Therefore,'- at each reversal of direction the die and blank contact at a different point, and thus,

since there are many reversals during the rolling of a blank, all parts of the blank receive substantially the same treatment. In practice I have found rotation one and one-fourth revolutions in one direction,-to one and one-half revolutions in the opposite direction, very effective. This, of course, ma be varied to satisfy any conditions whlch invite variation. ile the diagrammatic commutator in Fig. 10 requires a revolution 'of the commutator to complete a cycle of die movement, that is one movementforward and one backward, if desired there may be more contact plates, so that the die will complete two or more cycles for each revolution of the commutator. a mere matter of design, which will be understood by any skilled mechanic who puts this invention into practical use.-

In describing the operation of the machine shown in Fig. 1, I have explained how the operator may cause the oscillator operation of the machine. to be succeede by continuous rotation in one direction at some point in the course of rolling a blank. For example, I have suggested that this might be done when the sector C-D of the cam 132 comes into action; But I have also pointed out that if desired the step of rotating the die and blank continuously in one direction may be omitted. I shall now explain how all of*these variations in the mode of operation, in addition to others, may be employed in the machine shown in Fig. 8.

' If it be tinuouslyin one direction, the switch 361 is moved to contact 363, which is in connection with a switch 365. This switch may then be moved to contact 366 or contact 367. If it be moved to contact. 366,, the motor will desired to rotate the machine con- This is wire 356 and the switch 354, just as though the switch 361 wereoncontact 362and the arm 360 in contact with the segment 359. If

it be desired to'rotate the motor continuous- 1y forward, the switch 365 is moved to the contact 367.- y

Under certain circumstances it may bedesirable to movethe motorwery slightly, one

way or the other. F or example, in adjustin the machine it might be desirable to mo e the die-roll a few degrees. For this p rpose' I provide what- I call a jogging V s itch 368. This is represented as a flexible lever, poised between contact points 369 and 370. One of these points-is in connection with switch 353 and the other is in contact with"switch. 354. The switch 368 is inconnection rvith contact 364, and by means of switch 361 it may be put into connection with 2e line wire 356. Pressing the switch momentarily against contact 369 will jog the motor Slightly backward, w ile pressing it against the contact 370 willqog the'motor'forward.

Mention has been made of the clutch 336,

by which the two parts of shaft 334 are coupled. This clutch is operated by alever 375, pivotally mounted at 37 Gr. Ordinarily the two parts of shaft 334 remain coupled together, but in adjusting the'machine, or in case the machine becomes jammed, or for some other reason, it may be desirable to rotate the worm gear mounted on the shaft 330 independently of the motor and other main parts of the machine. In such a case-the clutch 336 may be opened and the shaft 334 rotated by a crank applied to the squared end of the shaft.

. In Fig. 8 the die-roll and blank holder, together with the timing gears, are covered by shields 380 and 381, the former being secured to the bearing 229 and the latter to bearing 236. These shields are so formed as to leave an opening at the front through which access to the blank holder is gained, so that blanks can be inserted in and removed from the blank holder. This opening is providedwith a, door 382, hinged to the shield 380. Referring now to Fig. 9 it will be seen that a nozzle 383, connected to the flexible tube 384, is set so that water discharged from'thel nozzle will play on and'between the teeth of the die-roll 242. This serves to cool the die, but its more articular function is to remove particles of orging scale which may have accumulated on the die. In, order to keep from spattering the hot blank .1- provide a shield or baflle 385, whichis carried by the hinged cover 382, so that as the cover is lifted the bafiie is removed with it. Instead of water, compressed air may be used for this purpose. Or both water an air may be usedconcurrently. In Fig. 8 two sets of pipes are shown, onelof which may be used for water and the other for air. 1

Hal have disclosed two preferred embodiments of my invention, it is not to be understood that the practice of my new method is limited to one or the other of these embodiments. Nor is it to be inferred that in the disclosed embodiments I limit myself to the particular constructions shown, for various modifications are possible while remaining within the purview of my present invention. \Vhat I claim as my invention is as follows:

1. The method of forming teeth on gears, which comprises rolling a toothed die against a heated gear blank, repeatedly reversing the direction of rotation but rotating 1 them farther in one direction than in the other, so that at each reversal a different part of the die and of the blank are in contact,'and concurrently pressing the die teeth into the blank. 2. The method of forming teeth on gears, which comprises rolling a toothed die against a heated gear blank, repeatedly revversing the direction of rotation but rotating them farther in one direction than in the other, so that at each reversal the die and blank will touch at a different point, maintaining invariable velocity ratio between the die and blank and concurrently pressing the die teeth into the blank. a

3. The method of forming teeth on gears which comprises rolling a toothed die against a heated gear blank and concurrently pressing the die teeth into the blank, repeatedly, reversing the direction of rotation for part of the time and then finishing the operation by continuous rolling in one direction.

4. The method of forming teeth on gears which comprises rolling a toothed die against a heated gear blank and concurrently pressing the die teeth into the blank, repeatedly reversing the direction of rotation for part of the time and then finishing the operation by continuous rolling in one direction, .maintaining invariable velocity ratio between the die and blank,

5, The method'of forming teeth on gears, which comprises rolling a toothed die against a heated blank and concurrently pressing-the die teeth into .the plastic blank, repeate y reversing the direction of rotation but rolling them farther in one direction than the other, sothat at each reversal the die and blank will touch in a different place, and finally rolling them for a while in one direction only. 7 j v 6. The method "of forming teeth on gears, which comprises rotating a heated gear blank incontact with a toothed die while maintaining invariable velocity ratio between them, keeping the blank and die constantly in contact but repeatedly reversing the direction of rotation, while pressing the blank and die together to cause the teeth of the die to sink intothe blank.

- teeth of the die to sink into the blank.

8. The method of forming teeth on gears, which comprises rotating a heated blankoin contact with a'toothed die and constantly pressing the die and blank against each other until the die teeth have sunk into the blank to a'desired distance from the agris of the blank, repeatedly reversing the direction of rotation of the blank, and concurrently maintaining an invariable velocity ratio between the die and blank.

9. The method of forming teeth on gears, which comprises rolling a rotary toothed die against a heated blank, repeatedly reversing the direction of rotation, rotating the blank three or less revolutions in each direction.

10. The method'of forming teeth on a heated blank, which comprises rotating the blank in contact with a toothed die, repeat-- edly reversing the direction of rotation, and

' together.

women in. The method of forming teeth on bevel 3b gears, which comprisesirotating-pa heated bevel gear blank in contact with a toothed die, repeatedly reversing the direction of rotation, while pressing the die and blank 12. The method of forming teeth on bevel gears, which comprises rotating a heated evel gear blank in contact-with a toothed die, repeatedly reversing the direction o'f'rotation, while pressing the die and blank to- 40 gether, rotating them .fyarther in one direc- L tion than the other so as to have the die and blank in contact at a. difierent point at each reversal.

13. The method of forming teethon gears,

which comprises rolling a rotary toothed die against a heated blank, repeatedly reversing the direction'of rotation while pressing them together, rolling them in one direction less than one revolutionfarther-than they roll 50 in the other direction. Y

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